Abstract

Neuropeptides synthesized by insect neurosecretory cells are engaged in several physiological process like immunity, feeding and reproduction so they deserve to be undertaken in subsequent experiments for discovery and manipulation regarding applied objectives. Due to importance of insect ability to utilize plant tissues, the present study was conducted to extract brain peptides in the fifth instar larvae of Pieris brassicae via High performance liquid chromatography and to identify their role in induction of digestive enzyme syntheses. Five peaks were determined and named as fractions 1, 2, 3, 4 and 5. The midguts of starved fifth larval instars were treated by each fraction of brain extract in vitro. The highest activities of α-amylase and lipase were found in the midgut treated by fractions 4 and 1, respectively while the fraction number 5 imposed the highest activities of glucosidases. Fraction 2 led to the highest activities of trypsin, chymotrypsin and elastase as the given serine proteinases as well as the two exopeptidases namely amino- and carboxypeptidases. Moreover, midgut treatments by different concentrations of TLCK (N-p-Tosyl-l-lysine methyl ester hydrochloride), TPCK (Tosyl phenylalanyl chloromethyl ketone), AEBSF (4-(2-Aminoethyl) benzenesulfonyl fluoride hydrochloride) and Acarbose significantly decreased the activities of α-amylase, trypsin, chymotrypsin and elastase by the calculated IC50 values of 0.287, 0.439, 0.288 and 0.361 mM, respectively. The findings demonstrated that different neuropeptides would be engaged in enzymatic release of P. brassicae hence, manipulation of peptide receptors can change physiological process of insects and opens a selective strategy to pest control.

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